The present invention relates generally to disk drives for storing data. More specifically, the present invention relates to a crash stop latch which temporarily inhibits the movement of an actuator assembly after the actuator assembly contacts an outer diameter stop for a ramp load, disk drive.
Disk drives are widely used in computers and data processing systems for storing information in digital form. In conventional Winchester disk drives, a transducer xe2x80x9cfliesxe2x80x9d upon an air bearing or cushion in very close proximity to a storage surface of a rotating data storage disk. The storage surface carries a thin film of magnetic material having a multiplicity of magnetic storage domains that may be recorded and read back by the transducer.
For a multiple disk, disk drive, a plurality of transducers are supported near the storage surfaces of the storage disks with a plurality of actuator arms. More specifically, each transducer is secured to one actuator arm with a load beam and a head suspension having a suspension gimbal. Typically, an actuator motor moves the actuator arms along a predetermined path to position the transducers relative to the storage surfaces of the storage disks. The combination of the transducers, the load beams, the head suspensions, the actuator arms, and the voice coil motor are commonly referred to as a head stack assembly.
The air bearing which enables each transducer to fly in close proximity to the surface of the disks, is created by air flow generated by rotation of the disks. When the disk rotation ceases, the air bearing dissipates and the transducers are no longer supported above the surfaces of the disks. Thus, when power is removed from a spindle motor that rotates the storage disks, the transducers come to xe2x80x9crestxe2x80x9d or xe2x80x9clandxe2x80x9d on the surfaces of the disks. Likewise, when the spindle motor is powered up, the transducers xe2x80x9ctake offxe2x80x9d from the surfaces of the disks. The landing and/or taking off from the storage disk can lead to loss of data and/or failure of the disk drive due to erosion or scarring of the magnetic film on the surfaces of the disks.
In some disk drives, the actuator motor positions each transducer over a landing zone as power is removed from the spindle motor. This inhibits the transducer from resting on an area of useful data storage during non-rotation of the storage disk. In one design, the actuator motor moves the transducers radially outward so that each head suspension slides onto a ramp positioned near an outer diameter of the storage disks. In this position, each transducer is xe2x80x9cunloadedxe2x80x9d from the storage disks. Typically, at the end of the desired range of motion, the head stack assembly contacts an outer diameter stop which inhibits additional outward movement.
Unfortunately, if the velocity of the head disk assembly is too great during the unloading of the transducers, the head stack assembly bounces off the outer diameter stop and the transducers swing back towards the disks. Depending upon the timing and the amount of impact force, this can cause rebounding of the head stack assembly away from the outer diameter stop and loading of the transducers back onto the decelerating storage disks. Additionally, the impact with the outer diameter stop can induce large pitch and roll vibrations of each transducer about the suspension gimbal. This can cause transducer contact with the storage disk and severe disk and/or transducer damage. Moreover, the transducers may end up stuck in an arbitrary location on the disks once rotation stops. This also can result in disk damage, transducer damage and/or total drive failure.
One attempt to solve the problem includes designing the outer diameter stop to absorb and dissipate as much impact energy as possible. This minimizes the amount of energy stored in the outer diameter stop during impact and minimizes the rebound energy returned to the head stack assembly. Additionally, power to the head stack assembly can be limited to prevent high speed impacts with the outer diameter stop. Unfortunately, neither approach is entirely satisfactory.
In light of the above, it is an object of the present invention to provide a reliable, simple, and efficient device which effectively inhibits the transducers from rebounding onto the disks during shut down. Still another object of the present invention is to provide a device which inhibits disk or transducer damage during unloading of the transducers. Yet another object of the present invention is to provide a latch for a disk drive which is relatively easy and cost effective to manufacture, assemble and use.
The present invention is directed to a latch for a disk drive that satisfies these objectives. The disk drive includes a storage disk, a head stack assembly and an outer diameter stop which limits the outward rotation of the head stack assembly. As provided herein, the latch selectively restrains the head stack assembly with a transducer positioned in a landing zone of the disk drive. More specifically, the latch includes a retainer that is movable between an engaged position and a disengaged position. In the engaged position, the retainer temporarily retains the head stack assembly near the outer diameter stop with the transducer in the landing zone. In the disengaged position, the retainer allows the head stack assembly to move away from the outer diameter stop.
Importantly, the latch inhibits the head stack assembly from rebounding away from the outer diameter stop after impact between the head stack assembly and the outer diameter stop. This reduces the potential of the transducer impacting the storage disk and reduces the potential for damage to the transducer and the storage disk. Additionally, the latch may allow the design requirements for the outer diameter stop for absorbing energy to be relaxed. Further, the latch may allow the actuator motor to move the transducer to the loading zone, using maximum available current, without rebounding the transducer back onto the decelerating storage disk.
Typically, the retainer includes a retainer hub and a latch hook. The retainer hub rotates around a latch pin relative to a drive housing of the disk drive. The latch hook engages or contacts the head stack assembly in the engaged position and inhibits rotation of the head stack assembly.
The latch also includes a mover which moves the retainer from the disengaged position to the engaged position. Similar to the retainer, the mover includes a mover hub that rotates around the latch pin relative to the drive housing. The mover can include a contact section which engages the head stack assembly. The engagement between the contact section and the head stack assembly causes the mover to rotate relative to the latch pin and move the retainer relative to the latch pin into the engaged position. The mover can also include a weighted segment which facilitates the mover rotating the retainer.
A connector connects the mover to the retainer. In one embodiment, the connector is a spring which connects the mover to the retainer. The spring allows for movement of the mover to result in movement of the retainer. Further, a spring constant of the spring is selected to adjust the amount of time the retainer remains in the engaged position.
Additionally, the latch includes a return connected to the retainer. The return moves the retainer from the engaged position to the disengaged position. This allows the head stack assembly to move the transducer from the landing zone. For ease of assembly, the return can be a spring that is attached to the retainer and the drive housing. The spring constant for the spring of the return is also selected to adjust the amount of time the retainer remains in the engaged position.
The present invention also includes a method for selectively restraining the transducer in the landing zone. The method includes the steps of providing a retainer, moving the retainer to the engaged position after the head stack assembly is moved to near the outer diameter stop and subsequently moving the retainer to the disengaged position.
Importantly, the latch inhibits the head stack assembly from rebounding away from the outer diameter stop after impact between the head stack assembly and the outer diameter stop. This reduces the likelihood of the transducer impacting the storage disk and reduces the potential for damage to the transducer and the storage disk. Further, with this design, the actuator motor can be allowed to move the transducers to the landing zone using maximum available current.